Impact fuze for a spin stabilized projectile

ABSTRACT

An impact fuze for a spin stabilized projectile of the type comprising a carrier for a detonator pellet, rotatable by spring means from a safe into an armed position, and a safety device in the form of an axially movable safety stud. The safety stud in a forward position locks the pellet carried in the safe position. The stud is displaceable by the acceleration on discharge of the projectile into a rear position in which it releases the carrier. The pellet carrier is positioned so that the centrifugal force acting on its center of gravity will oppose the inertial force due to spin acceleration. Thus the frictional forces arising between the pellet carrier and the safety stud is limited to prevent the stud jamming and preventing the fuze from being armed.

0 Muted States Patent 11 1 1111 3,732,825 Apotheloz 1 51 May 115, 1973 [54] IMPACT FUZE FOR A SPIN 2,448,228 8/1948 McCaslin et al ..102 80 x STABILIZED PROJECTILE 3,118,379 1/1964 Jasse I 2,999,461 9/1961 Apotheloz... Inventor: Robert Apotheloz, 8304 Walhsellen, 3,034,438 5/1962 Apotheloz et al. ..102/78 Switzerland 7 Primary ExaminerSamuel W. Engle [73] Assignee. Werkzeugmaschmenfabrlk Oerhkon Buhrle AG, Zurich, Switzerland A Wmdemth [22] Filed: June 22, 1971 [57] ABSTRACT [21] App]. N0.: 155,480 An impact fuze for a spin stabilized projectile of the type comprising a carrier for a detonator pellet, rotatable by spring means from a safe into an armed [30] Forelgn Apphcatmn Pnomy Data position, and a safety device in the form of an axially June 26, 1970 Switzerland ..9684/70 movable Safety The Safety Stud in a forward P tion locks the pellet carried in the safe position. The 52 US. Cl ..102/80, 102/84 Stud is displaceable y the accelfiration on discharge 51 Int. Cl. ..F42c 15/26 of the Projectile hm) a Year P which it 58 Field ofSearch ..102/78-80 releases The Carrie is Positimled that the centrifugal force acting on its center of gravity will oppose the inertial force due to spin accelera- [56] References cued tion. Thus the frictional forces arising between the UNITED STATES PATENTS pellet carrier and the safety stud is limited to prevent the stud jamming and preventing the fuze from being 3,162,126 12/1969 Weber et al. ..l02/78 arme 4 Claims, 7 Drawing Figures 4a If a 62 I 1; H

34D3/ ll; 35 35 37 PATEHTEU 51975 3 732.825

SHEET 1 OF 4 is, 7 \ix 10 7 I 67 /7 4 9 II 1@ H978 27 I5 57 i5 3 f5 W 50 "3&7 '13 -22 H Z2 1 I /9 ROBERT APOTHELOZ, Inventor PATENTEU HAY 1 51973 SHEET 2 BF 4 ROBERT APOTHELOZ, Inventor By M . orneys PATEHTEU 1 75 SHEET 3 BF 4 ROBERT APOTHELOZ', Inventor PATENTEU 1 5 3. 732 825 sum u. 0F 4 ROBERT APOTHELOZ, Inventor Attorneys IMPACT FUZE FOR A SPIN STABILIZED PROJECTILE The present invention relates to an impact fuze for a spin stabilized projectile of the type comprising a carrier for a detonator pellet, rotatable by spring means from a safe into an armed position, and a safety device in the form of an axially movable safety stud.

A known construction of this type of fuze for spin stabilized projectiles contains a safety device which does not release the pellet carrier until the acceleration of discharge has ceased. During discharge the acceleration of spin generates an inertial force that acts on the pellet carrier and may substantially increase the frictional forces between the pellet carrier and the safety stud. In the case of a safety deviceintended to release the pellet carrier before the acceleration of discharge has ceased, the said force of friction must not be allowed to increase since it might cause the stud to jam and thus prevent the fuze from being armed.

According to the present invention there is provided a body, a carrier for a detonator pellet, said carrier being rotatable by spring means from a safe into an armed position, and a safety device comprising an axially movable stud, in which the safety stud in a forward position locks the pellet carrier in the safe position, the safety stud being displaceable by the acceleration on discharge of the projectile into a rear position in which it releases the pellet carrier, and in which the pellet carrier is positioned so that the centrifugal force acting on its center of gravity will oppose the inertial force due to spin acceleration and thereby prevent the safety stud from jamming.

In a particular embodiment of the invention the pellet carrier is so contrived that in a projectile stabilized by right hand spin the center of gravity of the pellet carrier is on the right hand side, viewed in the direction of flight, of the line connecting the fuze axis and the axis of rotation of the pellet carrier, said connecting line subtending an acute angle at the center of gravity.

The drawing illustrates an embodiment of the subject matter of the invention. In the drawings:

FIG. 1 is an axial section of a fuze according to the invention along the line l-I of FIG. 2, showing the pellet carrier in a safe position;

FIG. 1a shows a selector pin in position for delayed action;

FIG. 2 is a cross section of the fuze of FIG. I along the line IIII;

FIG. 3 is a similar section of the fuze of FIG. 1 showing the pellet carrier in an armed position;

FIG. 4 is a longitudinal section along the line IV-IV of FIG. 3;

FIG. 5 is a diagrammatic representation of the fuze of FIG. I showing the forces acting on the center of gravity of the pellet carrier; and

FIG. 6 is a diagrammatic representation of the fuze of FIG. 1 showing the center ofgravity of the pellet carrier in a further position.

With reference to FIG. I a cylindrical plug 2 is inserted into a central blind bore 3 in the body I of a fuze. A sleeve 4 with a substantially closed top 5 is also contained in the bore 3 above the plug 2, the annular edge of the sleeve 4 resting on the top of the plug 2. A fuze head 6 axially traversed by a central bore 7 is screwed into the body I of the fuze and locates the sleeve 4 and the plug 2. A sleeve 8 is slidably movable inside the bore 7 in the head 6 of the fuze. A spring 9 is interposed between the top 5 of the sleeve 4 and a plug 10 positioned in the sleeve 8. The sleeve 8 is formed with a shoulder 11 which the spring 9 holds in contact with a corresponding shoulder 12 having a face perpendicular to the fuze axis inside the bore 7. A central bore extending upwards to the face 13 in the body of the fuze contains an explosive core 14 which extends down to the bursting charge (not shown) of the projectile.

A percussion pin 15 is attached to the plug 10 in the sleeve 8. The percussion pin 15 is guided in a bore through the top 5 of the sleeve 4 and projects through a chamber 17 enclosed by the sleeve 4 and through a face 16 of the plug'2 forming the bottom of the chamber 17 into a further bore 18 in the plug 2. The bore 18 leads into a cylindrical recess 19 in the plug, eccentrically located with reference to the longitudinal axis A of the fuze. The inner end 20 of the recess 19 (FIG. 2) is increased in diameter and has a circularly arcuate peripheral enlargement 21 which has its center on the longitudinal axis A of the fuze.

A detonation pellet carrier 22 in the form of a rotor, hereinafter referred to as the rotor, is contained in the recess 19 in the plug 2. The rotor 22 contains a central bore 23 which is open on the side of the rotor facing forwards. The underside 24 of the rotor bottom 25 is parallel to the face 13 in the body of the fuze. A ring 26 is positioned partly in the bore 23 so that a face of the ring projects from the leading face of the rotor 22. An arbor 27 is located in a further bore 28 in the plug 2 parallel to the bore 18 and secured against rotation by a key 69. The arbor 27 extends into the bore 23 in the rotor 22 and bears against the face 13 in the body I of the fuze. A coiled torsion spring 29 is contained in the bore 23 of the rotor 22 and embraces the arbor 27. One end 30 of the energized spring 29 bears against the ring 26 and is retained by the wall of a slit 33 connecting the bore 23 to a bore 32 in the rotor 22. The other end 31 of the spring engages a slit which is machined into a flange 34 on the arbor 27. The ring 26 is pressed against the bottom of the recess 19 by the thrust of the spring 29 which is also axially compressed.

The fuze includes a safety device which makes the fuze safe for transportation and handling. The device comprises a pin 35 and a safety stud 36. This device is contained in a bore 37 in the fuze body. The safety stud 36 projects into the arcuate enlargement 21 in the bore 20. With reference to FIG. 2 it will be seen that the rotor is formed with a gear quadrant 38 about its axis of rotation, and in its periphery with a concavity 39 that is concentric with the circumference of the safety stud 36. This concavity partly embraces the safety stud 36 and thus prevents the rotor 22 from rotating in either direction.

Referring to FIG. 4 the bore 40 in the body 1 of the fuze parallel to its axis contains an arrangement for delaying the action of the fuze. A cylindrical stem 41 in fixed at the bottom of the bore 40 and extends upwards into the bore. A sleeve 42 surrounding this member 41 is movable inside the bore 40 and in the illustrated position of rest the sleeve bears against a foot 43 of the member 41. A spring 44 is interposed between a shoulder 45 is the sleeve 42 and the rear end of a striker pin 46. The front end of the member4ll projects into a socket 47 in the back of the striker pin. The striker pin is coupled to the stem by locking balls 49 contained in bores 48 machined transversely into the wall of the striker pin at right angles to the striker pin axis. The locking balls are biased by the spring 44 into contact with a bevel face 50 in the stem 41 which is itself attached to the body of the fuze and the balls are thus held in coupling position with the stem 41. At the same time the balls 49 are retained by the internal wall of a second sleeve 51 which is likewise contained in the bore 40, and which is thus held in position by friction. This latter sleeve 51 has a bevelled end face 52 resting on the end face 53 of the sleeve 42 and its forward end 54 is of reduced diameter. When the fuze is armed the bore 55 in the rotor 22 axially aligns with the striker pin 46. This bore 55 contains a detonator pellet 56.

A selector pin 57 is provided in the plug 2 and extends perpendicularly to the fuze axis. In a manner not shown in the drawing this selector pin can be turned into either of two operative positions. The end of the selector pin 57 extending across the fuze axis contains an axial bore 58 for the reception of the pointed end of the percussion pin 15. When the selector pin is in position for direct action the percussion pin can pass through an opening 59 in the wall of the selector pin normal to the direction of the axial bore 58. When the selector pin 57 is turned through 90 into its alternative position for delayed action the passage of the point of the percussion pin 15 through the selector pin is obstructed, as shown in FIG. la.

A pocket 60 in the shape of an arc concentric about its axis of rotation is machined into the rotor22. This pocket 60 contains a filler 61 which is made ofa material of greater specific gravity than that of the material forming the rotor 22. The common center of gravity S of the rotor 22 containing the tiller 61 is not therefore located on the rotor axis D, but to one side of a line connecting the axis A of the fuze and the axis D of the rotor. The filler 61 has a socket 62 which in the safe position of the rotor 22 (FIG. 2) coincides with the axis A of the fuze. A detonator pellet 66 is contained in the rotor 22 in a bore 65 that is parallel to the axis of the fuze. The distance of this bore 65 from the axis of the rotor 22 equals the distance of the rotor axis from the axis of the fuze.

The gear quadrant 38 on the rotor 22 meshes with a gear wheel that is mounted on a pin 64 rotatably mounted in the plug 2. A gear train comprising a pinion 67 in the chamber 17 forms a transmission for cooperation with an escapement lever 68, thus constituting an escapement delay train which in a known manner retards the rotation of the rotor 22.

In projectiles stabilized by right hand spin the fuze containing the plug 2 will experience an acceleration of spin about the axis A of the fuze in the direction P in FIG. 5. A consequent inertial force F will have a tangential component T with respect to the axis of rotor rotation D. At the same time a centrifugal force Z will act on the center of gravity S. This center of gravity S is located on the right hand side of a line V connecting the fuze axis A to the rotor axis D, the line V subtending an acute angle a at the center of gravity. To assist in an understanding of later explanations the center of gravity S is shown in FIG. 6 in a position which differs from its actual position. In this instance the connecting line between the axes A and D subtends an obtuse angle ,8 at the center of gravity. The center of gravity S of the rotor 22 experiences a centrifugal force Z and the tangential component T of an inertial force F The described arrangement functions as follows:

Before the projectile is fired the rotor 22 will be in the safe position shown in FIGS. 1 and 2, in which the axis of the bore 65 is offset from the axis A of the fuze. Immediately after having been fired the projectile (not shown) is accelerated, the rotor 22 being displaced to the rear against the resistance of the spring 29 until the underside 25 of the rotor bottom 24 finds support on face 13 in the body of the fuze. When the rotor is thus supported the force of inertia acting parallel to the axis of rotor rotation D at a point offset from the axis cannot cause the arbor 27 to bend and the rotor to tilt.

In the case of a spin stabilized projectile the rotor 22 will be subjected to a further inertial force F, for as long as the spin of the projectile is accelerated. The position of the center of gravity S is therefore so chosen, as illustrated in FIG. 5, that the tangential component T of this inertial force F will oppose the thrust of the spring 29 as well as the centrifugal force Z. The contact pressure between the safety stud 36 and the concavity 39 in the rotor 22 is thus reduced, permitting the safety stud 36 to slide reliably rearward into the bore 37 for releasing the rotor 22. If the center of gravity were located as shown in FIG. 6 the tangential component T and the centrifugal force F would be codirectional and additive and the contact pressure would be increased. The safety stud might thus be frictionally jammed and unable to release the rotor for arming the fuze.

If the selector pin 57 is turned into position direct" the rotor 22 cannot immediately turn into arming position when the locking pin 36 withdraws because the point of the percussion pin 15 is forced by inertia to the rear into the socket 62 in the filler 61. When the projectile has left the barrel and forward acceleration ceases the spring 29 pushes the rotor 22 forward until the ring 26 bears against the bottom of the bore 19. At the same time the spring 9 forces the sleeve 8 into its forward position in contact with the shoulder 12 in the fuze head 6. The point of the percussion pin 15 is withdrawn from the socket 62 in the filler 61 and the rotor 22 is now free to turn. The spring 29 assisted in the case of spin stabilized projectiles by centrifugal force turns the rotor 22 anti-clockwise (in FIG. 2) out of the safe" into the armed" position, (FIG. 3). This rotary motion proceeds at a speed determined by the gear train and escapement lever 68 according to the time the projectile is desired to remain safe after leaving the bore of the barrel. When the fuze is armed the cylindri cal concavity 39 in the rotor 22 lies adjacent the pinion 63 and the axis of the bore 65 containing the detonator pellet 66 aligns with the axis A of the fuze. When the fuze strikes the target the sleeve 8 is pushed into the body of the fuze and the percussion pin 15 penetrates the pellet 66, thereby initiating the detonation of the bursting charge of the projectile through the explosive core 14.

If the selector pin 57 had been set to delay," as shown in FIG. 10, then the percussion pin 15 could not have ignited the pellet 66 upon impact of the projectile. After having been released by the safety plug 36 the rotor 22 had turned into armed position in the abovedescribed manner in which the axis of the second striker pin 46 aligns with the axis of the bore containing the detonator pellet 56. Upon impact the two sleeves 42 and 51 are thrown forwards, notwithstanding the braking force applied to them by the locking balls 49, and the spring 44 is further energized. When the delay of the fuze has nearly expired the spring 44 can move the sleeve 42 backwards and a free space is thus again opened up between the sleeve 51 which is in its extreme forward position and the sleeve 42 that is again in contact with the foot of the stem 41. The pressure of the bevel face 50 on the stem 41 now forces the balls 49 into this open space, thereby releasing the striker pin 46 to be propelled forward by the spring 44. The balls 49 are deflected by the oblique end face 52 on the front sleeve 42 into the interior of the socket 47 in the striker pin which can move forward unimpeded to ignite the detonator pellet 56. This communicates through the space between the rotor 22 and the bottom of the recess 19 with the detonator pellet 66, igniting the latter by its flash and thus causing the bursting charge to be detonated.

I claim:

1. An impact fuze for projectiles stabilized by righthand spin, said fuze having a longitudinal axis and comprising a body; a cylindrical pellet carrier mounted within said bodyvfor rotation around a carrier axis parallel to said fuze axis; a detonator pellet carried by said carrier; said carrier having a pocket therein on one side of a line connecting said fuze axis and said carrier axis; said pocket being filled with a material having a greater specific gravity than the material forming said carrier; the center of gravity of said carrier thereby being located at a point such that lines therefrom to said fuze axis and said carrier axis form an acute angle; spring means for rotating said carrier about the axis thereof from a safe position to a loaded position; and safety means for selectively preventing or allowing said rotation of said carrier, said safety means comprising an axially movable stud urged in a first position to friction contact with said carrier, and mounted for axial movement to a second position out of said friction contact with said carrier upon acceleration during discharge of said projectile; whereby centrifugal force acting on said center of gravity of said carrier opposes the inertial force due to spin acceleration of said carrier during said discharge, such that said friction contact is released and said safety means is prevented from jamming during said acceleration.

2. An impact fuze as claimed in claim 1, wherein said carrier is mounted for axial movement against said spring means during said acceleration; said carrier having a rear face normal to said fuze axis; said body having a rear face parallel and adjacent to said rear face of said carrier; said carrier face and said rear face of said body being in contact during said acceleration.

3. An impact fuze as claimed in claim 2, wherein said body has a forward face adjacent the forward end of said carrier; said spring means comprises a precompressed torsion spring surrounding said carrier axis; and further comprising a ring mounted on the forward end of said torsion spring and urged thereby into contact with said forward face of said body, said ring providing the only contact between said carrier and said body when said carrier rotates about said carrier axis.

4. An impact fuze as claimed in claim 1, wherein said body has a forward face adjacent the forward end of said carrier; and spring means comprises a precompressed torsion spring surrounding said carrier axis; and further comprising a ring mounted on the forward end of said torsion spring and urged thereby into contact with said forward face of said body, said ring providing the only contact between said carrier and said body when said carrier rotates about said carrier axis. 

1. An impact fuze for projectiles stabilized by right-hand spin, said fuze having a longitudinal axis and comprising a body; a cylindrical pellet carrier mounted within said body for rotation around a carrier axis parallel to said fuze axis; a detonator pellet carried by said carrier; said carrier having a pocket therein on one side of a line connecting said fuze axis and said carrier axis; said pocket being filled with a material having a greater specific gravity than the material forming said carrier; the center of gravity of said carrier thereby being located at a point such that lines therefrom to said fuze axis and said carrier axis form an acute angle; spring means for rotating said carrier about the axis thereof from a safe position to a loaded position; and safety means for selectively preventing or allowing said rotation of said carrier, said safety means comprising an axially movable stud urged in a first position to friction contact with said carrier, and mounted for axial movement to a second position out of said friction contact with said carrier upon acceleration during discharge of said projectile; whereby centrifugal force acting on said center of gravity of said carrier opposes the inertial force due to spin acceleration of said carrier during said discharge, such that said friction contact is released and said safety means is prevented from jamming during said acceleration.
 2. An impact fuze as claimed in claim 1, wherein said carrier is mounted for axial movement against said spring means during said acceleration; said carrier having a rear face normal to said fuze axis; said body having a rear face parallel and adjacent to said rear face of said carrier; said carrier face and said rear face of said body being in contact during said acceleration.
 3. An impact fuze as claimed in claim 2, wherein said body has a forward face adjacent the forward end of said carrier; said spring means comprises a precompressed torsion spring surrounding said carrier axis; and further comprising a ring mounted on the forward end of said torsion spring and urged thereby into contact with said forward face of said body, said ring providing the only contact between said carrier and said body when said carrier rotates about said carrier axis.
 4. An impact fuze as claimed in claim 1, wherein said body has a forward face adjacent the forward end of said carrier; and spring means comprises a precompressed torsion spring surrounding said carrier axis; and further comprising a ring mounted on the forward end of said torsion spring and urged thereby into contact with said forward face of said body, said ring providing the only contact between said carrier and said body when said carrier rotates about said carrier axis. 